STOCKHOLM (AP).- A Swedish artist who angered Muslims by depicting the Prophet Muhammad as a dog was assaulted Tuesday while giving a university lecture about the limits of artistic freedom.

Lars Vilks told The Associated Press a man in the front row ran up to him and head-butted him during a lecture, breaking his glasses but leaving him uninjured. It wasn't immediately clear what happened to the attacker.

Vilks has faced numerous threats over his controversial drawing of Muhammad with a dog's body, but Tuesday's incident was the first time he has been physically assaulted.

Earlier this year U.S. investigators said Vilks was the target of an alleged murder plot involving Colleen LaRose, an American woman who dubbed herself "Jihad Jane," and who now faces life in prison. She had pleaded not guilty.

Vilks said a group of about 15 people had been shouting and trying to interrupt the lecture before the incident at Uppsala University.

Many of them stormed the front of the room after the attack and clashed with security guards as Vilks was pulled away into a separate room, he said, describing the scene as "complete chaos."

"A man ran up and threw himself over me. I was head-butted and my glasses were broken," Vilks said before hanging up for questioning by police.

Uppsala University spokeswoman Pernilla Bjork said Vilks was showing a provocative film with sexual content to the crowd when the attacker ran up and hit him in the face with his fists.

Swedish news agency TT said police detained two people during the commotion. Uppsala police spokesman Jonas Eronen said he couldn't comment because he didn't have enough information about the incident.

University officials said there had been a peaceful demonstration by Muslims outside the university before Vilks started to speak, and that about 250 people attended his lecture. Bjork said the university had been in contact with police and security guards before Vilks' lecture to ensure his safety.

"We think it is our task as a university to be able discuss difficult issues," she said. "We think it is very unfortunate that this has resulted in violence."

Vilks made his rough sketch more than a year after 12 Danish newspaper cartoons of the prophet sparked furious protests in Muslim countries in 2006.

A Swedish newspaper printed the drawing, leading to further protests, and revived a heated debate in the West and the Muslim world about religious sensitivities and the limits of free speech.

It also led to numerous death threats against Vilks, who was temporarily moved to a secret location after al-Qaida in Iraq put a $100,000 bounty on his head in September 2007.